The installation of the DVG-1120M is quick and easy, thanks in large part to the thorough documentation provided with the device. The graphic below is taken from the D-Link website and serves as a basic connection diagram to follow during installation.
I won’t go into every step of the installation, but will cover the connections to be made to get up and running. My broadband connection is of the cable variety, so I first needed to connect the WAN connection on the DVG-1120M to my Motorola Surfboard cable modem, using the blue network cable provided. The LAN connection on the DVG-1120M was then connected to my D-Link DI-704 broadband router, and the phone connection was connected to my standard phone. After a few minutes, the DVG-1120M made the necessary initial connection to the VoIP server and the phone made a distinctive ring to let me know it was ready for use. It was that easy to setup... No software to install, no network settings to configure, just plug and play!
The image below shows my specific installation. From left to right you have a Morex Cubid 3688 case containing a VIA EPIA M10000 mainboard, which is connected to the D-Link DI-704 broadband router, which is connected to the D-Link DVG-1120M VoIP Gateway, which is in turn connected to the Motorola Surfboard cable modem. Not pictured, but of equal importance is a GE 2.4 GHz cordless phone with caller id.
With everything connected, I immediately picked up the phone and started to test that aspect of the device. I made a local call, followed by a long distance call, and was amazed by the clarity of both. My expectations for the voice performance were obviously set too low, as every aspect of my calls was equal to what I was used to on my traditional landline. Calls connected quickly (I expected some sort of lag as the server processed the call), voice volume was at a comfortable level, and nothing seemed any different from my landline. Besides the fact that none of the people called recognized my new number on their caller id, no one was able to distinguish anything that would indicate I wasn’t calling from a traditional landline phone.
After a few weeks of use, and numerous phone calls later, I am still highly impressed with the performance of the DVG-1120M. One less than perfect aspect of the voice performance is an occasional low volume hum, only detectable during a lull in the conversation. To be honest, I occasional get similar issues when using my normal phone, and since I’m calling the same people with the VoIP phone, perhaps its an issue on their end.
After making a few phone calls, I jumped back onto the internet to see how that functioned now that there was one more device between the computer and the world wide web. As soon as I launched Internet Explorer I was relieved to see that the connection was still intact... Off to a good start so far. I then tested the speed of the connection using the New York City based hub of SpeakEasy.Net’s speed test (always best to test on your closest hub). The chart below details my speed test results with and without the DVG-1120M installed, providing both the upload and download speeds. From left to right, the three sets of results represent my cable connection without the DVG-1120M installed, with the DVG-1120M installed while no phone calls are in progress, and with the DVG-1120M installed while a phone call is in progress. As charted, the results are based on the average of three tests run during "off-peak" internet hours and while no phone calls were in progress, so that as little would interfere with the results as possible.
As you can see from the data above, although the upload speed was virtually unaffected, a 10% drop in download speed was experienced when the DVG-1120M was installed, but not being used for a phone call. But, take a look at the speeds achieved while a phone call is in progress! Wow! That is roughly a 99% drop in speed! A phone call has a serious impact on the speed of the internet connection, and it is apparent in real world use. While browsing simple sites that generally load immediately I am reminded of the sad old days of dial-up when pages loaded painfully slow.
Conclusion:
My initial concerns regarding the statement that "Voice service is prioritized over the data traffic" proved to be well founded. In fact, I underestimated the impact a phone call would have on the speed of my internet connection, as I would have never guessed it could take a line which has benchmarked download speeds as high as 6600 kbps down to a mere 75 kbps.
In addition to the massive speed drops, I experienced another problem. During large uploads or downloads (via HTTP or FTP), whether phone calls are in progress or not, I am frequently forced to try several times, as the transfers get stuck part way through and fail to resume within a timely manner. I have tried tweaking a few registry settings using TCP Optimizer, including the Max MTU and TCP Receive Window, but I have yet to compensate for this problem.
My first experience with VoIP phone service has been an extremely positive one so far. The D-Link DVG-1120M VoIP Gateway is a major factor in my enthusiasm for VoIP, as it provided me with a quick and easy installation and excellent phone call quality. The extent to which my internet speed decreased surprised me, but I guess the packets sent for voice transmission use some serious bandwidth (major understatement). Relying on a VoIP phone in an an environment where internet connectivity was critical isn’t a good idea, but if you can plan your phone calls around your need for net speed, it may work out.
In general, reviews are focused towards informing consumers about products they may be interested in purchasing. For the most part, anyone receiving the D-Link DVG-1120M has probably subscribed to a VoIP service, and probably had little choice in the hardware they received. This review probably won’t influence any purchasing decisions, but hopefully provided a little more information for people a general interest in VoIP.
Final Rating (3.5 out of 5 stars):  
Pros:
• Excellent voice quality
• Provides all the features of your typical phone (caller id, call waiting, etc)
• Quick and easy installation
• Thorough documentation
Cons:
• Seriously Impacts internet connection speed when phone is in use
• Experience lags during download/upload that didn’t exist without device
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